I've often felt that Judaism, especially Reform Judaism, is the perfect religion for this synthesis*. It was born out of the belief that a religion must be rational in order to be true. It's always rejected the supernatural, and felt that the deepest meaning can be found in religion when we acknowledge that our ancient, sacred texts are speaking in metaphors, not expressing scientific facts.
* I'll also acknowledge that the fact that I was born a Reform Jew probably has a lot to do with this view. I'll admit a bit of bias here!
But, I've never felt that Reform Judaism and rationality were precisely the same thing. I know of some Reform Jews who believe things which I think are most definitely not rational (although, they'd disagree, I imagine). And, I certainly know people of other denominations and religions who are very rational, as well. Being rational is not a Jewish thing, or a Reform Jewish thing.
I think that at least some people, after speaking to me (or reading my stuff, etc), might not realize that. I've often had responses to these ideas that amount to "Well, I don't believe that - I'm a Christian." As if Christianity demands a literalist belief, but Judaism allows for more non-literalism.
I'm not educated enough to know if one religion is actually better than the other, in this regard. Like I said, I feel as if Reform Judaism is stronger here, but that's quite possibly just my bias. But, even if one religion, or one sect, might be more rational than another, that doesn't make it the exclusive domain of that one. It really does cut across all lines. I was reminded of that by an article I read by Michael Ruse, a professor Philosophy at Florida State. that anyone might still believe that the Bible, specifically the Adam and Eve story, is literally true:
The cover article of this month's Christianity Today is on the subject of Adam and Eve. Could humans be descended from one single pair or not? Really, Christians should be over this one by now. They should have been over it by Christmas of 1859, a month after Charles Darwin published his "Origin of Species." As he said there, "light will be thrown on the origin of man and his history."
To those of us in the rationalist camp, believing that the Adam and Eve story is historical fact, a full century and a half after Darwin (and, after a slew of other types of discovery which effectively disprove the historicity of the first parts of the Bible), would be exactly like believing the world is flat, or that the sun orbits around the earth.
But, importantly, Ruse goes on to make it clear that disbelieving in the facts in the Genesis story (and more) is not the same as being non-religious:
The great British theologian John Henry Newman saw clearly that the essential truths of the Christian faith remain unchanged, but that, given new knowledge in each age, they need constant reinterpretation and updating.
I really like that phrasing. I want my religion to be based on essential truths, not on arbitrary facts. Even if those facts happen to be true, they still shouldn't be a fraction as important as those truths! And, I'd hate to stake my entire religious belief system (and, in my case, my career!) on one particular set of facts. Because, then my religion is only as sound as my facts - and that's rarely very sound!
Let me try to put that a tiny bit differently. Forget about what fact we're talking about. If there is one fact, any fact, whose dis-proof would shatter your religion, then your religion, pretty much by definition, isn't very strong.
And, it really doesn't matter which religion that is. In that, we're very much all the same.